1. Field of Invention
The invention is pertinent to a brush holder stay of a rotary electric machine that is used in, for example, a driving part of each of various kinds of actuators installed in an automotive vehicle, etc.
2. Description of Related Art
In general, among that type of rotary electric machines, there is the one wherein a commutator is integrally fitted onto a rotating shaft rotatably supported on a casing; a brush supported on the casing side is in sliding contact with the commutator; and, by doing so, the power is supplied to the coil disposed around the outer periphery of the rotating shaft. In this case, the brush is supported so that it may freely move out from and into a holder portion integrally formed on a ring-like stay part where a through hole is formed in order to pass through the rotating shaft. In the brush holder stay equipped with the stay part and the holder portion, it sometimes has a structure wherein a bearing is integrally fitted into the through hole of the stay part and, one end portion of the rotating shaft is supported by the bearing. In such an arrangement, sometimes, of a sintered oil-impregnated bearing constructed by sintering metal powder (e.g. copper powder) and impregnating oil into fine cavities of the sintered material is used as the bearing.
In the rotary electric machine using the conventional sintered oil-impregnated bearing, in a case where the dynamo-electric machine is placed in a high-temperature environment, it is possible that the oil will ooze from the sintered material due to the difference between the thermal coefficient of expansion of the sintered material (bearing) and that of the oil impregnated in the sintered material. In a case where the rotary electric machine has been placed under a high-temperature condition like that, as illustrated in FIG. 12, the oil oozes from the sintered oil-impregnated bearing 13 and oozes into the through hole 15a of the stay part 15 of the brush holder stay 14. In this case, the oil that has oozed out is assumed to pass through the corner portion formed by a holder portion 16, projectingly formed on the ring-like stay part 15, and the stay part 15, due to capillary action, around to the outside-radial side of the holder portion 16 and from the outside-radial side into the holder (undesignated). In the case where the oil has oozed into the holder portion 16, there is the possibility that the oil will ooze between the brush 17 and the commutator 18. When that occurs, problems, such as the electrical conduction between the brush 17 and the commutator 18 deteriorating and the brush 17 wearing abnormally occurs. In this respect, there exists a need to address the problems that the invention is to achieve.
The invention has been made under the above-described circumstances and has an object to solve the above-described problems, the object being to provide a brush holder stay of a rotary electric machine, the brush holder stay comprising a ring-shaped stay part that has formed therein, on its inner-radial side, a through hole having fitted thereinto a sintered oil-impregnated bearing for supporting a rotating shaft and a holder portion that is integrally formed on the stay part and that accommodates therein a brush slide in contact with a commutator fitted over the rotating shaft in such a manner that the brush freely moves out from and into the holder portion, wherein the stay part is provided with a concave groove portion located on at least one side of the holder portion in the circumferential direction and the concave groove portion is formed with an end wall on the inner radial side and having a depth parallel to the axial direction of the rotating shaft so as to serve as an oil pool for an oil path which goes from the through hole toward the outer-radial side of the holder portion via the stay part.
And, by doing like that, it is possible to prevent the occurrence of the inconvenience that the oil goes into the inside-radial side of the holder portion and thereby attaches onto the brush.
In the above-described arrangement, it can be arranged that the end wall is formed so as to be connected to an inner-radial side end surface of the holder portion.
Further, in such an arrangement, it can be arranged that the concave groove portion has substantially the same length as the that of the holder portion in the radial direction.
Further, in that arrangement, it can be arranged that the concave groove portion is formed between the holder portion and a terminal-fixing portion formed adjacent to the holder portion.
Further, the invention provides a brush holder stay of a rotary electric machine, the brush holder stay comprising a ring-shaped stay part that has formed therein on its inner-radial side a through hole having fitted thereinto a sintered oil-impregnated bearing for supporting a rotating shaft and a holder portion that is integrally formed on the stay part and that accommodates therein a brush slide in contact with a commutator fitted over the rotating shaft in such a manner that the brush freely moves out from and into the holder portion, wherein the stay part is provided with a concave groove portion located on inner-radial side end surface between the holder portion and the through hole and concave in the outer-radial direction of the rotating shaft so as to serve as an oil pool for an oil path which goes from the through hole toward the holder portion.
And, by doing such, it is possible to prevent the occurrence of an inconvenience that the oil goes into the inside-radial side of the holder portion and thereby attaches onto the brush.
In the above-described arrangement, it can be arranged that the brush holder stay of the invention has a structure where the brush holder stay has formed thereon a pair of holder portions diametrically opposing each other and the paired holder portions are disposed in a positional relationship wherein they oppose each other substantially in the up-and-down direction relative to a horizontal rotating shaft axis.